1. Technical Field
The present disclosure relates to a wireless communication apparatus, and more particularly, to an apparatus and method for removing an interferer signal in a wireless communication apparatus.
2. Discussion of the Related Art
Because many wireless communication service providers use a limited wireless frequency spectrum, interference between wireless communication system has been increasing. For example, when different wireless communication systems use adjacent regions in the wireless frequency spectrum, interference may often occur.
FIG. 1 is a functional block diagram of a conventional wireless communication receiver 10. Referring to FIG. 1, the wireless communication receiver 10 includes an antenna 11, a duplexer 13, a low noise amplifier (LNA) 15, a surface acoustic wave (SAW) filter 17, a down-conversion mixer (or a down frequency converter) 19 that also receives a local oscillator signal fLO, and a low pass filter (LPF) 21.
This LNA 15 amplifies a radio frequency (RF) signal input through the antenna 11 and the duplexer 13. The SAW filter 17 filters the RF signal output from the LNA 15 to pass only an in-band signal and outputs a filtered RF signal X1 to the down-conversion mixer 19. The RF signal includes a desired signal and an undesired signal, that is, an interferer signal also called a jammer signal.
The down-conversion mixer 19 converts the output signal of the SAW filter 17, that is, the filtered RF signal X1 into a baseband signal X2 using the local oscillator signal fL0. The LPF 21 filters the baseband signal X2 output from the down-conversion mixer 19 to pass only a channel signal X0, that is, the desired signal WS shown FIG. 2A and outputs the channel signal X0 to a modem (not shown).
Referring to FIGS. 1 through 2C, the interferer signal, hereinafter, referred to as a “jammer signal”, included in the output signal X1 to the down-conversion mixer 19 is transferred as it is to the output signal X2 of the down conversion mixer 19. Accordingly, the LPF 21 is designed to have a bandwidth for removing the jammer signal included in the baseband signal X2, as illustrated in FIG. 2C. Most of the jammer signal is removed by the LPF 21 and only some jammer leakage is included in the filter output X0.
Generally, wireless communication receivers receive an RF signal including a desired signal and an undesired signal, that is, a jammer signal. The jammer signal interferes with the reception of the desired signal. In code division multiple access (CDMA) wireless communication receivers, the phase noise and linearity of a voltage controlled oscillator is substantially determined according to the magnitude of a jammer signal and not that of a desired signal, that is, a CDMA signal.
In other words, design specifications of elements of a receiver, such as the LNA 15, the down-conversion mixer 19, and LPF 21, become very complicated because of the jammer signal. As a result, designing the elements of a receiver is difficult and is expensive.